Surgeons often use metal rods of predetermined diameter, e.g. in the range of 3/16ths to 5/16ths inch, in splinting portions of the human skeleton, e.g. to effect fusing of adjacent vertebrae in the spine. The skeleton, however, is multi-curved, and the rod must be bent to conform to the curvature of the bone in order to maximize affixation between the splinted portions of the skeleton. For example, in many instances, a surgically implanted splint includes respective parallel legs, preferably disposed in a common plane, and an arcuate bridge connecting the legs, disposed in a plane transverse to that of the legs. When implanted, the legs of the splint extend along opposing sides of the respective portions of the skeleton, and with the arch angled towards the exterior, bridging the skeleton, to maintain the legs in position to fix the relative disposition of the skeletal portions.
An example of such an implant is shown in FIGS. 1A and 1B. Specifically, a splint implant 100 is disposed to fix the relative disposition of respective vertebrae C1 and C2 at the base of a patient's occiput 102. Implant 100 includes respective parallel legs 106 and 108, connected by a generally U-shaped bridge 110. As best seen in FIG. 1A, respective legs 106 and 108 are disposed in parallel, extending along opposing sides of vertebrae C1 and C2 for a predetermined distance above and below the vertebrae. As best seen in FIG. 1B, bridge 110 is bent at an angle transverse to the plane of legs 106 and 108, coupling legs 106, while accommodating the patient's anatomical structure.
Historically, pre-bent splinting implants have been employed by surgeons. However, commercially available pre-bent implants are provided in specific sizes (e.g. small; medium; and large). Because the splinting implants do not typically meet morphological fit requirements, surgeons have generally reconfigured the bone to fit the implant. This process typically involves removing, e.g. grinding or cutting away, portions of the bone, and tends to be both time consuming and traumatic to the patient. Further, while the general configuration of a splinting implant for particular portions of the skeleton can be determined by x-ray and imaging techniques, in many instances it is desirable to confirm the desired configuration of the implant by visual inspection of the skeletal portions at issue. Accordingly, it is desirable that the surgeon be able to shape bendable metallic rods to form custom implants during surgery to meet the specific anatomical fit requirements of a patient.
Attempts have been made to form implants in the operating room during surgery by bending rods into the desired configuration. However, bending was effected employing pliers, vices, and hammers. While rod benders are, in general, known, the devices typically can bend the rod only to a single particular radius and are not shielded to protect against debris flying in the event that a rod breaks, but nonetheless tend to be relatively complex devices, including closed holes, cervices, and interstices, in which blood or tissue is often retained, and are difficult to disassemble for cleaning. Such devices are thus difficult to clean and sterilize e.g. by autoclaving, for use in the operating room.
Significantly, the prior techniques for custom bending of rod to form implants in the operating room, have tended to nick, scratch, gouge, or kink the surgical implant. Such marring tends to form stress risers, and to lead to early fatigue failure of the implant. Specifically, in situ, the splint implant is subject to relatively high stresses. While healthy bone typically replaces itself, thus accommodating wear from such stresses, that is not the case with a metal implant; normal stresses tend to fatigue the metal of the implant. Marring, such as any nicks, scratches, gouges, or the like in the implant, tends to produce very high stresses at the root of the mar, tending to make the implant more susceptible to bending and ultimate failure.
Fabrication of the implant in the operating room has also tended to involve a significant period of time, e.g. 20 to 25 minutes.
Accordingly, there is a need for an apparatus for custom forming of implants from metal rod in the operating room, quickly and economically, without marring the surface of the rod, and which is simple and readily disassemblable, and autoclavable to ensure proper sterilization.